The role of ouabain-sensitive adenosine triphosphatase in the stimulating effect of thyrotropin on the iodide pump of the rat thyroid.

Abstract

Previous studies (2) indicated that a (probably indirect) relationship existed between thyroidal ouabain-sensitive adenosine triphosphatase (ATPase) activity and iodide transport; they were also compatible with the idea that the known stimulating effect of thyrotropin (TSH) on the thyroidal iodide pump may be mediated by activation of ouabain-sensitive ATPase. In the thyroids of 23 normal rats fed Purina Laboratory Chow, ouabain-sensitive ATPase activity was found to be 70 ± 3 (SE) pmoles inorganic phosphate (Pi) per g wet tissue per hr, or 6 % of that of total ATPase. The thyroid serum l'adioiodide concentration ratio (T/S) in 12 of these rats averaged 44. Factors which increased the output of endogenous TSH [1% NaC104 in the drinking water, low iodine intake, injections of propylthiouracil (PTU)] raised the activity of thyroidal ouabain-sensitive ATPase, both in absolute terms (up to over 500 μmoles Pi per g per hr) and as the percentage of that of total ATPase (up to 20% or more). Except for the NaClO4...